Commit-ID: adcfe76c61732a0dda5116206c3741733491f1e8 Gitweb: https://git.kernel.org/tip/adcfe76c61732a0dda5116206c3741733491f1e8 Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> AuthorDate: Tue, 30 Jan 2018 19:36:38 -0800 Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> CommitDate: Tue, 20 Feb 2018 16:22:00 -0800 torture: Default jitter off when running rcuperf The purpose of jitter is to expose concurrency bugs due to invalid assumptions about forward progress. There is usually little point in jitter when measuring performance. This commit therefore defaults jitter off when running rcuperf. You can override this by specifying the kvm.sh "--jitter" argument -after- the "--torture rcuperf" argument. No idea why you would want this, but if you do, that is how you do it. One example of a conccurrency bug that this jitter might expose is one in which the developer assumed that a given short region of code would be guaranteed to execute within some short time limit. Such assumptions are invalid in virtualized environments because the hupervisor can preempt the guest OS at any point, even when the guest OS thinks that it has disabled interrupts. Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> --- tools/testing/selftests/rcutorture/bin/kvm.sh | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/tools/testing/selftests/rcutorture/bin/kvm.sh b/tools/testing/selftests/rcutorture/bin/kvm.sh index f3c3d33150a0..56610dbbdf73 100755 --- a/tools/testing/selftests/rcutorture/bin/kvm.sh +++ b/tools/testing/selftests/rcutorture/bin/kvm.sh @@ -179,6 +179,12 @@ do checkarg --torture "(suite name)" "$#" "$2" '^\(lock\|rcu\|rcuperf\)$' '^--' TORTURE_SUITE=$2 shift + if test "$TORTURE_SUITE" = rcuperf + then + # If you really want jitter for rcuperf, specify + # it after specifying rcuperf. (But why?) + jitter=0 + fi ;; *) echo Unknown argument $1 -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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